1) Login to the Admin section of WHMCS.
2) In the navigation menu, roll your mouse over Clients tab, then click View/Search clients
3) Click the name of the client, who owns the domain you want to manage.
4) Click the Domains tab.
5) As per the official WHMCS documentation, “You'll also see a row labeled Registrar Commands with options such as Renew, Modify WHOIS, Get EPP Code, etc...” Clicking those options allow you to make changes with their registrar.
